Traditionally, most commercially available inkjet printers have a print engine which forms part of the overall structure and design of the printer. The body of the printer unit is usually constructed to accommodate the printhead and associated media delivery mechanisms, and these features are integral with the printer unit.
This is especially the case with inkjet printers that employ a printhead that traverses back and forth across the media as the media progresses through the printer unit in small iterations. Typically, the reciprocating printhead is mounted to the body of the printer unit such that it can traverse the width of the printer unit between a media input roller and a media output roller, with the media input and output rollers forming part of the structure of the printer unit. It may be possible to remove the printhead for replacement, however the other parts of the print engine, such as the media transport rollers, control circuitry and maintenance stations, are usually fixed within the printer. Replacement of these parts is not possible without replacement of the entire printer.
As well as being rather fixed in their design construction, printers employing reciprocating type printheads are relatively slow, particularly when performing print jobs of full colour and/or photo quality. This is due to the fact that the printhead must continually scan the stationary media to deposit the ink on the surface of the media and it may take a number of swathes of the printhead to deposit one line of the image.
Recently, ‘pagewidth’ printheads have been developed that extend the entire width of the print media. The printhead remains stationary as the media is transported past its array of nozzles. This increases print speeds as the printhead no longer needs to perform a number of swathes to deposit a line of an image. Instead, the printhead deposits the ink on the media as it moves past at high speeds. With these printheads, full colour 1600 dpi printing at speeds of around 60 pages per minute are possible. Such speeds were unattainable with conventional inkjet printers.
The flow rate of ink from the cartridge to a pagewidth printhead is higher than the flow rate to a scanning printhead. The number of simultaneously actuating nozzles to be supplied with ink is far greater in a pagewidth printhead. Accordingly, the outlet valve from the cartridge needs to handle a relatively large flow. Unfortunately, a bigger outlet valve can tempt users to tamper with it prior to installation. Inserting a pen nib or similar into the valve may open valve and cause ink leakage. Sophisticated printers can track the ink levels in a cartridge using the drop volume, the number of actuations of the relevant nozzles, and the known ink volume of a full cartridge. Ink leakage prior to installation will compromise the print engine controller's (PEC's) ability to monitor remaining ink levels. If the PEC allows the cartridge to completely run dry, the nozzles will de-prime and risk damage from actuator burn out.